This invention relates to coil fitting systems for fitting coils in the slots of an iron core of an electric rotary machine by forcing the coils into the slots, and more particularly it is concerned with improvements in or relating to a coil fitting system for fitting, in a single operation, into the slots a plurality of coils arranged in such a manner that a portion of an end portion of one coil overlaps a portion of an end portion of another coil.
An iron core of an electric rotary machine constitutes a stator which is formed at its central portion with an inner opening for receiving a rotor therein, and a multiplicity of slots open in the inner opening. A multiplicity of coils wound beforehand are required to be fitted in the slots in a predetermined relation. Fitting the coils wound beforehand in the slots of the electric rotary machine of the aforesaid construction is effected by forcing the coils through one side of the inner opening by a pressing member. This type of coil fitting system generally has the following construction.
The coil fitting system comprises a multiplicity of blades arranged axially in the form of a ring as a whole. The ring has a diameter which is substantially equal to the diameter of the inner opening of an armature core in which the slots open, so that the armature core can be force fitted on the ring of blades. The blades adjacent one another in the ring of blades define therebetween gaps which are each equal to or slightly smaller than the opening of each slot in width. The coils of a predetermined shape wound beforehand are hung and held in a predetermined position after being slipped through the gaps. Meanwhile the ring of blades has in the interior a coil stripper serving as a pressing member guided for movement in an axial direction. When the coil stripper is moved in the axial direction after the predetermined shape of coils wound beforehand are hung and held in position in a predetermined position in the ring of blades and the armature core is force fitted about the ring, the coils are moved by the action of the coil stripper and fitted in the slots in the armature core.
In the coil fitting system of the prior art of a this construction, a set of plurality of coils is held in position at coil end portions by the ring formed by the plurality of blades, so that the set of coils is force fitted in the slots in the armature core in one operation. In this system, when coil end portions do not overlap, no trouble occurs. However, when an attempt is made to fit coils whose end portions overlap in one operation step, a coil end portion of one coil held between the coil stripper and a coil end portion of another coil might be compressed and suffer damage.
To obviate this problem of the prior art, Japanese Utility Model Publication No. 44881/76 proposes to use a coil stripper of a special shape. More specifically, the coil stripper is provided with two pressing surfaces including a first pressing surface for pressing against the coil end portion of one coil, and a second pressing surface for pressing against the coil end portion of another coil arranged in such a manner that one portion thereof overlaps one portion of the coil end portion of the one coil pressed by the first pressing surface. The second pressing surface holds the coil pressed thereby in a direction in which the coils are pressed. By this arrangement, the coil end portions overlapping each other are fitted in the slots in the armature core in a condition in which they are spaced apart from each other, thereby obviating the aforesaid problem of the prior art.
However, the use of the coil stripper of this construction would have some problems that should be solved before it is put to practical use. One of them involves the condition of the coil which is force fitted by the second pressing surface or the ease with which fitting of the coil by the second pressing surface is effected. More specifically, the end portion of the coil fitted by the first pressing surface would be moved by the first pressing surface to one side of the end portion following completion of the fitting operation and pushed in a radial direction by an outer edge surface of a portion constituting the first pressing surface, to be shaped thereby. However, as described hereinabove, the first pressing surface remains inside the ring of blades, so that the coil end portion of the coil which is force fitted by the first pressing surface would block an upper portion of each of the gaps defined by the blades. Thus the coil which is force fitted by the second pressing surface would be forced against the upper portions of the blades by the coil which is force fitted by the first pressing surface during the coil fitting operation. What results would be an obstruction to smooth fitting of the coils in the slots, so that it might become difficult to fit the coils or the coils might suffer damage, even if they are successfully fitted. This phenomenon would be marked particularly when the coils have a large pitch or a high volume ratio in the slots. The second problem is that when the coil stripper is restored to its original position following completion of operation of fitting the coils in the slots, the coil stripper might bite into the coils. As described hereinabove, the coil end portion of the coil which is force fitted by the first pressing surface is pushed in the radial direction by the outer edge surface of the portion constituting the first pressing surface, to be shaped thereby. Thus the coil end portion of such coil would press strongly against the outer edge surface and a tension would develop. If the coil stripper is pulled back to restore it to its original position when the coil end portion of the coil is in the aforesaid relation to the outer edge surface of the portion constituting the first pressing surface, a portion of the coil would also be pulled back by the outer edge surface of the portion constituting the first pressing surface, with the result that a portion of the coil would be bitten between the outer edge surface and an inner lateral surface of each blade juxtaposed against the outer edge surface.